Interlace or Progressive?!?!

[Pro.Killer]

How do i know?!!?

i need a sure way to know, not just by looking!

[Mug Funky]

unfortunately human error is rife in the DVD authoring business, and other formats like DV will switch between interlaced and progressive on a per-block basis.

so the only real way to know is by looking - DV will not explicitly say it's interlaced or not, and mpeg-2 flags can be wrong quite often (and are further complicated when film sources are hard-telecined and encoded interlaced).

it's not that difficult to determine, and if you're working an automated setup where you don't have time to look at everything, simply specify interlaced as default and you wont have many problems. it's a little less compression efficient on progressive material, but aside from that there's jack-all difference.

if you're just backing up DVDs, then watch the disc on a standalone with an interlaced TV and you'll get a good idea of what you're in for - smooth motion = interlaced, jerkier = film/telecine (telecine has a kind of jittery fast-slow-fast-slow motion about it).

[LordRPI]

Originally posted by Mug Funky

if you're just backing up DVDs, then watch the disc on a standalone with an interlaced TV and you'll get a good idea of what you're in for - smooth motion = interlaced, jerkier = film/telecine (telecine has a kind of jittery fast-slow-fast-slow motion about it).

Sometimes it is even hard to tell on an interlaced TV. A good rule of thumb is to use DVD2AVI (or a newer equivalent). You can find some documentation towards the bottom of this page (http://www.everwicked.com/content/DivX_5_Guide/content-03.php).

[Mug Funky]

the problem with DVD2AVI or other programs that read the flags in the stream is that quite often the flags are just plain wrong.

you'll get telecine titles that are hard-telecined and encoded as 29.97 interlaced, you'll get pure progressive PAL films with interlaced flag set, and more disturbingly you'll get pure interlaced video with the stream marked as progressive. there are literally thousands of wrong titles out there, so the only thing you can do is look frame by frame in Virtualdub or DVD2AVI (this doesn't show every frame i don't think), or train your eyes to tell between different frame types on an interlaced TV.

of course, field-shifted PAL will look more-or-less like progressive on an interlaced TV. it never hurts to watch a DVD before backing it up, after all.

[LordRPI]

Maybe my eyes aren't that sensitive, but it's really hard to tell if something on an interlaced TV is interlaced or not. To display something progressive on an interlaced TV it has to be telecined anyway. Your progressive computer monitor will do a much better job of showing interlacing artifacts, regardless of what the flags are. Telecined video at 29.97 frames per second will look interlaced on a prograssive monitor. Pure interlaced video marked as progressive will look interlaced anyway. It's really hard to tell interlaced video on TV set that relies on interlacing to show the picture. Maybe all my TV's stink.. who knows.